Paul,
Page 339 in your owner's manual lists the battery specifications, there is also chart in your Wiring Diagrams supplement booklet that lists standard and optional chassis battery configurations.
Likely, the reason that your battery boost is not functioning is because the Big Boy isolator relay is not working, probably needs to be cleaned. Also, could be why your chassis batteries didn't last very long, they're not charging from shore power.
In Coach Assist->Common Problems->Support Systems, you'll find a white paper that discusses the charging system for your coach and an article that contains instructions for cleaning the Big. Cleaning instructions can also be found on YouTube.
-Scott
